Two-piece cans are the most common type of metal container used in the beer and beverage industry, as well as for aerosol and food packaging. The two-piece container consists of a unitary body, including a side wall open at one end with an integral end wall at the other end. The integral end wall is usually formed to a domed-shaped configuration to increase the overall strength of the container. An annular portion is usually formed to a special configuration between the center dome panel of the bottom wall and the side wall that defines a reduced diameter support for the container and also provides a nesting feature for nesting with the end of an adjacent container, which is seamed to the open end thereof.
An exemplary bottom profile for a drawn and ironed container that has achieved a remarkable degree of commercial success is disclosed in U.S. Pat. No. 4,685,582. The container disclosed therein also includes an upper end portion that has a reduced neck so that a second end panel or end having a smaller diameter can be utilized to enclose the open-ended drawn and ironed container.
In most cases, containers that are used for beer and carbonated beverages are formed from a flat aluminum disc to an outside diameter of 2-11/16th inch (referred to as a "211-container") and the upper open end is reduced in diameter to form a 209-neck (2-9/16th inch) or any other smaller diameter, such as a 2071/2-neck, a 206-neck, and even a 204-neck or smaller so that smaller diameter ends can be utilized in the finished package.
An important competitive objective in the packaging industry is to reduce the total can weight as much as possible, while maintaining its strength and performance, in accordance with industry requirements. For pressurized contents, such as soft drinks or beer, the integral bottom end wall of the container usually has the same metal thickness gauge as the initial disc and the side wall is reduced through a drawing and ironing process to a thickness approaching one-third of the thickness of the original metal disc. Accordingly, to minimize overall weight, the can top or end panel that forms the second piece of the two-piece can is made as diametrically small as possible, while still maintaining the structural integrity of the container, the functionality thereof, and an aesthetically-pleasing appearance.
In the manufacture of containers of this type, a sheet of stock material of predetermined thickness is fed to a cupping press, wherein circular discs are cut from the stock material and are transformed into cups having a diameter which is considerably larger than the ultimate diameter of the finished container.
The preformed cups are then transferred to a container-forming apparatus, commonly referred to as a "bodymaker" wherein the cup is aligned with a punch carried on a reciprocable ram which cooperates with a plurality of spaced ironing dies and a doming mechanism located at the end of the path of the punch. During the forming process, the punch initially cooperates with a redraw assembly in which the shallow cup is redrawn to a smaller diameter that has an internal diameter approximately equal to the internal diameter of the ultimately-finished container and a height that is greater than the height of the original cup.
Each cup then passes through a series of ironing dies having progressively reduced diameters so that the side wall of the container is progressively reduced in thickness, while the height of the container increases. At the end of the stroke for the punch or ram, the end of the container is forced into a predetermined configuration to form an integral end wall that has a central inwardly-domed panel and a specially-configured peripheral annular bead or support portion. The drawn and ironed container is then trimmed to a selected height and coated and labeled, and a reduced tapered neck is produced on the open end.
To produce a container that can be price competitive and yet meet the rigid industry requirements, particularly for pressurized contents, such as beer and carbonated beverages, the Assignee of the present invention has developed a die necking operation for sequentially reducing the upper open end of the container to a smooth die neck configuration. This is done through a plurality of steps until the desired reduction for an end, such as a 206- or 204-end, is achieved. This process is disclosed in U.S. Pat. No. 4,774,839, incorporated herein by reference. A container of the type having a bottom profile, such as disclosed in U.S. Pat. No. 4,685,582, and a smooth die neck configuration illustrated in the above-referenced patent has increased strength characteristics and the overall aesthetic appearance has been enhanced.
In order to further enhance the overall appearance of the two-piece drawn and ironed container, it has also been proposed to deform the container side wall to produce a fluted appearance, such as disclosed in U.S. Pat. Nos. Des. 283,011 and DES 290,688.